Two empirical indoor-to-outdoor path loss models to facilitate femtocell network deployment are derived from continuous wave power measurements. A large set of indoor-outdoor transmitter locations in two residential streets in an urban setting and operating at 900 MHz, 2 GHz, 2.5 GHz and 3.5 GHz have been used to derive the model parameters by using singular value decomposition (SVD). The path loss models have been compared and validated against existing models as well as independent measurement data and good comparison is shown. The root mean square error of the residual path loss data obtained from the measurement data, which directly relates to the channel shadowing characteristics, is compared and validated with known results and has led to new model parameters being proposed. The expressions derived from the modelling can be used in system-level simulators, as well as for shadowing interference analysis of two-tier heterogeneous networks operating in indoor-outdoor scenarios at or close to the operating frequencies considered. In this study, the models extend the operating frequency range compared to related models and introduce SVD as a convenient means of deriving parameters from measured path loss data
